Chicago adds rat birth control to rodent-fighting arsenal

A pilot program on the South Side to combat rodents will use 25 enclosed boxes that provide a nonlethal liquid contraceptive bait in a feeding tube to make the rats infertile.

A pilot program on the South Side to combat rodents will use 25 enclosed boxes that provide a nonlethal liquid contraceptive bait in a feeding tube to make the rats infertile. (Antonio Perez / Chicago Tribune)

In a new pilot program on the South Side, the city's Streets and Sanitation Department set up 25 enclosed boxes that provide a nonlethal liquid contraceptive bait in a feeding tube to make rats infertile.

Crews set up the ContraPest bait boxes, made by Arizona-based SenesTech Inc., earlier this month on the perimeter of a garbage transfer station in the South Lawndale community. The boxes' effectiveness will be monitored for six months before officials consider a citywide expansion.

The new program is an additional rat-control measure in the city, which also uses poisonous pellets and dry ice to combat rats.

"Our job here is to control and eliminate what we see out there," said Josie Cruz, deputy commissioner of rodent control.

The city budgeted $5 million this year for rodent control operations, including 22 crews and supplies, Cruz said. The white, triangular-shaped, fertility-reducing bait boxes cost a total of $15,000, Cruz said.

Residents often spot rodents scurrying down alleys and sidewalks in Chicago. Last fall, Orkin named Chicago the top rattiest city among 50 U.S. cities, based on the number of rodent treatments the company performed from Oct. 1, 2015, to Sept. 30, 2016.

But city officials say they have the rodent issue under control, pointing to the response time of five days or less to address a complaint made to 311. The number of rodent complaints has decreased by 2.4 percent from Jan. 1 through July 24 this year — when there were 20,846 complaints — compared with the same time period last year, when 21,365 complaints were logged, according to city data.

City officials credit fewer sightings to public outreach campaigns, including signage and brochures with reminders on how to eliminate food sources for rats, along with traditional baiting methods of putting poisonous pellets in rat burrows.

In addition, the city plans to use dry ice again as a rat-fighting tool. Dry ice chunks, which are placed into a rodent burrow, then melt into carbon dioxide and suffocate the rodents.

The city had tested dry ice from August through December last year at various parks but discontinued its use after it wasn't registered as a pesticide, said Sara McGann, Streets and Sanitation spokeswoman. Now that the Environmental Protection Agency has approved of its use for pest control, the city will decide when it will resume using dry ice, where and for how long, she said.